I’m running a 5e campaign in a Homebrew setting. My BBEG is a rather powerful being kind of... locked in a fixed, repeating point in time. I've taken quite a few liberties here, but in order to continue to influence the world around him, he has been taking "avatars", in a sense—essentially, he slaps a splinter of his consciousness/mind/soul/essence/whatever on top of the (willing) vessel's own consciousness, resulting in rather, uh... mentally unstable enemies. Now to the actual question at hand.
One of these avatars was killed by my ever-so-illustrious party, and a particularly angry PC curb stomped her poor little head in. However, the party did nothing with or to the body to ensure she would stay dead. I, capable of limitless cruelty when the mood strikes me, have decided I want to resurrect her—but ideally, as a construct. I'm sure there's some other way around the head-smashy bit, but I want her to be angry.
So, what I want to know is, can I do this, and if so, how? Everything I could find on Warforged seemed to imply that I couldn't drop an already existing soul into one, let alone golems.
How can a soul be resurrected or transferred into a construct body?